Method for positioning bucket loader

ABSTRACT

A bucket loader having pivotally mounted lift arms with a bucket pivoted on the free end of the lift arms by motor means actuated in opposite directions through a control valve. The control valve is actuated in either direction in response to (1) automatic sensing means for maintaining a predetermined angular relation relative to a fixed reference plane and (2) actuation of a manual control lever in either direction from a neutral position. The automatic sensing means incorporates mechanism for changing the control angle of the bucket relative to the fixed reference plane when the valve is controlled by the lever and thereafter maintaining the bucket at the new control angle. The mechanism further includes interlocking means between the manual control and the automatic sensing control when the bucket is pivoted to a maximum roll-back position to neutralize the control means and mechanism for rendering the sensing means inoperative when the lift arms are lowered beyond a desired lowermost position.

United States Patent 1191 Seaberg et al.

1451 July 29,1975

[ METHOD FOR POSITIONING BUCKET LOADER [75] Inventors: David H. Seaberg, Burlington; Paul J. Purdy, New London, both of Iowa [73] Assignee: J. 1. Case Company, Racine, Wis.

[22] Filed: Mar. 31, 1972 [21] Appl. No.: 239,876

Related U.S. Application Data [62] Division of Ser. No. 58,588, July 27, 1970, Pat. No.

Primary ExaminerRobert J. Spar Assistant ExaminerRoss Weaver Attorney, Agent, or Firm-Dressller, Goldsmith, Clement & Gordon, Ltd.

[57] ABSTRACT A bucket loader having pivotally mounted lift arms with a bucket pivoted on the free end of the lift arms by motor means actuated in opposite directions through a control valve. The control valve is actuated in either direction in response to (1) automatic sensing means for maintaining a predetermined angular relation relative to a fixed reference plane and (2) actuation of a manual control lever in either direction from a neutral position. The automatic sensing means incorporates mechanism for changing the control angle of the bucket relative to the fixed reference plane when the valve is controlled by the lever and thereafter maintaining the bucket at the new control angle. The mechanism further includes interlocking means between the manual control and the automatic sensing control when the bucket is pivoted to a maximum roll-back position to neutralize the control means and mechanism for rendering the sensing means inoperative when the lift arms are lowered beyond a desired lowermost position.

3 Claims, 12 Drawing Figures PATENTED JUL29 I975 SHLI NMN

SHEET PATENTED JUL 2 9 I975 PATENTED JUL 2 9 I975 SHEET METHOD FOR POSITIONING BUCKET LOADElR This is a division of application Ser. No. 58,588, filed July 27, 1970, now U.S. Pat. No. 3,713,557 issued 1-30-73.

BACKGROUND OF THE INVENTION The present invention relates generally to material handling equipment and more particularly to improved method for controlling the position of a bucket supported on a boom.

In conventional earth moving equipment, such as bucket loaders, the machinery generally consists of one or more lift arms pivotally carried on a vehicle with a bucket pivoted on the free end of the lift arms. Generally, the lift arms are raised and lowered on the vehicle by a fluid motor having fluid supplied thereto through a control valve while the bucket is pivoted on the end of the lift arms through an additional fluid motor having fluid supplied thereto through a further control valve.

In normal operation the bucket is positioned in a dig" position and is forced into a pile of material by forward movement of the vehicle. The bucket is then pivoted or rolled back on the boom or lift arms for the vehicle with sufficient force to break out the mass of material within the bucket from the remainder of the pile. Subsequently, the lift arms are elevated a sufficient distance to raise the bucket above the ground and the vehicle is driven to some other location. Upon reaching the subsequent location, the bucket is pivoted to a dumping position where the contents are discharged, after which the operation is repeated.

In an operation such as this, it is important that the bucket be maintained at a level position while the loader is driven from the first location to the second to prevent the material or contents from being spilled. In other instances, it may be desirable to maintain the bucket in a position other than a level position, for example, when transporting bulky material which extends beyond the confines of the bucket. Additionally, it is extremely important that the control mechanism for controlling the position of the bucket on the boom incorporate mechanism which will prevent pivotal movement of the bucket beyond a predetermined rollback position to insure that the contents will not be dumped on the operator, which could not only cause injury to the operator but also could damage the vehicle. In other instances, it may be desirable to automatically maintain the bucket in a return-to-dig position.

While various control mechanisms have been proposed for preventing the bucket from being pivoted beyond a predetermined maximum roll-back position, maintaining the bucket at a level position or automatically returning the bucket to a return-to-dig position, the versatility of the devices heretofore known is rather limited.

SUMMARY OF THE INVENTION The present invention contemplates a linkage system for interconnecting a unit. a manual control lever and a valve for controlling the flow of fluid to and from a fluid ram which pivots the unit on a boom. The linkage system is arranged to (I) automatically maintain the unit at a desired angular orientation relative to a fixed reference plane; (2) manually controlling the unit at any time; (3) setting a new desired orientation for the unit through actuation of the manual lever; (4) preventing the unit from being pivoted beyond the rollback position; and (5) rendering the valve responsive to only the manual control lever when the unit is pivoted to the dump position or the boom reaches a predetermined lowered position.

Stated another way, the present invention contemplates control means for controlling valve means cooperating with a fluid ram to pivot a bucket in opposite directions on one end of a boom which, in turn, is piv oted at its opposite end on a vehicle. The control means includes a link having an intermediate portion connected to the valve means with manual means and automatic sensing means respectively connected to oppo site ends of the link to move the opposite'ends in opposite directions from a neutral position. The automatic sensing means cooperates with the bucket and actuates the valve means in an appropriate direction and maintains a desired angular orientation of the bucket relative to a fixed reference plane.

The manual control means disconnects the sensing means from the valve means upon being actuated to (1) allow manual control of the bucket and (2) to change the desired angular orientation of the bucket relative to the fixed reference plane and, when the manual control means is moved to a neutral position, the sensing means becomes operative to maintain the bucket at a new angular orientation.

The control means further includes mechanism operatively interconnecting the manual means and the sensing means for moving both ends of the link and the valve to a neutral position and prevent pivotal movement of the bucket beyond the roll-back position by either the sensing means or the control lever. This mechanism also includes switch means cooperating with the boom to allow movement of the bucket beyond the roll-back position when the boom is below a predetermined lowered position.

The method of the present invention contemplates manually actuating the control valve and interrupting the connection between the bucket and the valve through the sensing means to move the bucket to a desired angular orientation relative to a fixed reference plane; neutralizing the control valve and setting the sensing means to correspond to the desired angular orientation and subsequently actuating the valve with the sensing means to automaticallly maintain thfi bucket at the desired angular orientation. Subsequent, actuation and release of the manual control while the bucket is within predetermined limits will automatically reset the desired angular orientation and the control valve is neutralized by the sensing means when the bucket reaches a maximum angular orientation relative to the reference plane.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS FIG. 1 shows a side elevational view of a vehicle mounted implement, having the present control mechanism incorporated therein;

FIG. 2 is an enlarged, fragmentary side elevation view of the control linkage, constructed in accordance with the present invention;

FIG. 3 is an enlarged fragmentary plan view of the linkage system constructed in accordance with the present invention;

FIG. 4 is a vertical elevational view generally along lines 44 of FIG. 2;

FIG. 5 is a plan view taken generally along line 55 of FIG. 4;

FIG. 6 is a schematic perspective view of the valve control system of the present invention;

FIG. 7 is a sectional view of a spring assembly;

FIG. 8 is a schematic of an electric circuit;

FIG: 9 is a fragmentary perspective view of the linkage; and

FIGS. 10 thru 12 schematically illustrate the various positions of a portion of the linkage associated with the control valve in its various operating positions.

DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.

FIG. 1 of the drawings discloses a vehicle 10, such as a tractor, supported on endless tracks 12. The vehicle 10 has an upright support 14 which supports a loader assembly or implement, generally designated by the reference numeral 16. The implement 16 consists of a lift arm or boom 18 pivotally supported at one end thereof by means of a pivot pin 20 on the upright support 14. A bucket 22 is pivotally supported at the other end of the boom or lift arm by means of a further pivot pin 24.

The implement or loader assembly 16 and more particularly the lift arm or boom 18 is adapted to be raised and lowered relative to the support 14 through motor means 26 which illustratively include a cylinder 28 pivoted at 30 on the upright support 14 and a piston rod 32 pivoted at 34 on an intermediate portion of the boom 18. Pressured fluid is adapted to be suppled to the head and rod ends of the cylinder through conduits (not shown) and the flow of fluid to and from the opposite ends of the cylinder 28 is controlled by a valve 36 (FIG. 2).

While only one upright support 14, one lift arm 18 and one fluid ram 26 are shown, it will be appreciated that two such supports, lift arms and fluid rams are respectively located on opposite sides of the longitudinal center of the vehicle 10.

The pivotal movement of the bucket 22 about pin 24 is controlled by motor means 40 in the form of a fluid ram having its piston rod 42 pivotally connected at 44 to the boom 18 and its cylinder 46 trunnion mounted at 48 on a link 50. The link 50 forms part of a compound linkage and is pivotally connected at 52 to the boom 18 while the opposite end is pivotally connected to a second link 54, which in turn is pivoted on the bucket at 56. Thus, the boom 18, the bucket 22 and the links 50 and, 54 cooperate to define a parallelogram linkage system and relative extension and retraction of the piston rod 44 and cylinder 46, by supplying pressured fluid from a further valve or control means 58 (FIG. 2), will change the configuration of the parallelogram to pivot the bucket 22 on the boom 18.

As was indicated above, in most instances it is desirable to maintian the bucket in a level condition, as shown in FIG. 1, while in other instances it may be desirable to automatically maintain the bucket at some other position relative to a fixed reference plane. In addition, it has become substantially essential to prevent the bucket from being rolled-back beyond a predetermined maximum roll-back position thereby obviating the possibility of dumping the contents of the bucket onto the operator and the vehicle when the lift arms are moved to an extreme raised position.

According to the present invention, all of the above is accomplished through a single linkage system which is (l) capable of preventing pivotal movement of the bucket beyond a predetermined maximum roll-back position, and (2) automatically maintaining the bucket at any desired angular orientation between two extreme or maximum angles with respect to a fixed reference plane. Additionally, the present invention incorporates a manual control mechanism which is capable of being actuated at any point in the cycle and, when actuated, will automatically render the automatic control inoperative. According to another aspect of the invention, the manual control system cooperates with the automatic control system in such a manner that the control angular position of the bucket may be established by the manual control. Furthermore, the manual and automatic control systems are operatively interconnected in a manner that the control valve will be moved to a neutral position any time the bucket reaches the maximum roll-back angle. All of the above is accomplished by a single linkage system which will now be described.

The linkage system or control system includes a link (FIGS. 4 and 5) maintained in a neutral position by a pair of spring assemblies 72 connected to opposite ends thereof by pivot pins 74. The spring assemblies are connected at their lower ends to brackets 76 extending from a support housing 78. The two centering spring assemblies or biasing means for normally maintaining the links 70 in a neutral position are identical in construction and only one will be described.

By way of example, with particular reference to FIG. 7, each spring assembly 72 includes a housing 80 closed at one end by a member 82 having a rod 84 fixedly secured thereto. The internal opening in the housing 80 receives a pair of telescoping members 86 and 88, each of which has a flange 90, 92 extending radially adjacent the outer end thereof. A spring 94 is interposed between the flanges and biases the flange 92 into engagement with the member 82 while biasing flange into engagement with an abutment 96 cooperating with a closure member 98 received in the open end of the housing 80.

A rod 100 has one end threadedly received in an internal opening 102 defined in the inner telescoping member 88 while the opposite end of the rod 100 extends through an opening 104 defined in the abutment 96. A pair of lock nuts 106 are received on the threaded rod and one of the nuts engages the under surface of the abutment 96. The end 108 of assembly 72 is connected to the link 70 while the opposite end 109 is connected to the bracket 76.

Thus, extension of the end 108 will telescope the lower member 88 and the abutment 96 will maintain the upper member 86 in a fixed location to compress the spring 94. Alternatively, retraction of the end 108 will force the abutment 96 as well as the outer member towards the opposite end of the spring assembly to again compress the spring 94. The cooperation of the two spring assemblies with the opposite ends of the link 70 will maintain the link in a neutral position, for a purpose which will be described later.

Any movement of either end of the link 70 from the neutral position will be transmitted through a linkage to the control valve or control means 58. For this purpose, a shaft 110 FIGS. 2 and 5) is supported for rotation about a fixed axis with one end of the shaft connected to the control valve through an arm 112 and a link 114. The opposite end of the shaft 110 is connected to an intermediate portion of the link 70 through a radially extending arm 116 and a bolt 118. In this manner, movement of either end of the link 70 in either direction from a neutral position (shown in FIG. 4) will rotate the shaft 110 in the appropriate direction and thus actuate the control valve 58 in opposite directions from a neutral position and pivot the bucket in opposite directions. The movement of respective ends the link 70 in opposite directions from a neutral position is accomplished through a manual control means 120 connected to one end of the link and an automatic sensing means 122 connected to the opposite end of the link, as will be described.

The manual control means 120 (FIGS. 4 and 6) is capable of controlling the pivotal movement of the bucket as well as the raising and lowering of the boom 18 on the vehicle. For this purpose, the control means includes a control lever 124 supported for rotation about an axis defined by a shaft 126 as well as about a second axis 128 perpendicular to the axis of the shaft 126. During movement of the control lever in opposite directions from a neutral position about shaft axis, the shaft 126 will be rotated and the rotation thereof will be transmitted through an arm 130 (FIGS. 4 and 5) connected to the shaft with a link 132 interconnecting this arm with an arm 134 fixed to the end of a hollow shaft 136. The opposite end of the hollow shaft 136, which is concentric with shaft 110, is connected through an arm 138 (FIG. 2) and a link 140 to the lift control valve 36. The connection of the manual control lever 124 to the bucket valve 58 includes a cross shaft assembly 142 rotatably supported on a shaft 143 and having an arm 144 extending therefrom with the arm 144 connected to the lever 124 through a link 146. The opposite end of the shaft assembly 142 is connected, through an arm 150 and an adjustable rod 152, to the link 70. Thus, pivotal movement of the control lever 124 about axis 128 will move the left-hand end, as viewed in FIG. 4, of the link 70 in opposite direction from the neutral position to actuate the control valve 58.

The automatic sensing means 122, discussed above includes a shaft 200 (FIGS. 1, 4 and 6) supported for rotation about a fixed axis. One end of the shaft is connected to the opposite end of the link 70 through a friction device 202 and first linkage means including a link 204 and adjustable rod 206. The friction device 202, which may be a clutch or a brake, includes a first element 210 fixed for rotation with the shaft and a second element 212 rotatable relative to the shaft with the link 204 fixed to the second element 212.

When the friction device 202 is coupled, rotation of the shaft 200 in opposite directions from a neutral position will move the right-hand end of the link 70 (as viewed in FIG. 4) in opposite directions from a neutral position to actuate the control valve 58. The rotation of the shaft 200 is controlled by pivotal movement of the bucket 22. For this purpose, the opposite end of the shaft 200 is connected through a second linkage means to the bucket 22 so that pivotal movement of the bucket 22 will be transmitted to the shaft and rotate the shaft in appropriate direction to move the link 70.

The second linkage means includes an arm 220 extending from the shaft and connected to a first arm 221 of bell crank 222 through an adjustable rod 224. The bell crank 222 is supported for rotation about the pivot pin 20 defining the pivot axis for the lift arms or boom 18. A second arm 226 of the bell crank 222 is connected'through a telescoping; linkage 228 and a parallelogram linkage 230 to the link 50. As more clearly shown in FIG. 1., the parallelogram linkage 230 includes first and second links 232 and 234 pivotally interconnected at 236 with the link 232 pivoted on the lift arm 18 by a pin 238 and the link 234 connected by a pivot pin 239 to the link 50. The pivot pins 238 and 239 are respectively spaced from the pivot pin 52. The links 232 and 234 combine with the bucket link 50 to provide a signal output to link assembly 228 that defines angular change of the bucket. This is necessary since the angular movement of link 50 is not the same as that of the bucket.

The telescoping linkage 228 includes an outer tubular member 240 slidably receiving an inner tubular member 242, which has a nut 244 threaded on an inter mediate portion thereof.

The automatic sensing means 122 further includes means for defining first and second limit positions for the shaft 200 which, respectively, (1) accommodate movement of the bucket without rotation of the shaft 200 and (2) define a maximum angular or roll-back position of the bucket relative to a fixed reference plane. This mechanism further includes biasing means for urging the shaft to the first position with the biasing means accommodating rotation above the shaft to wards the second position. In the second position, the sensing means automatically operates on each end of the link to place both ends of the link in a neutral position and thereby neutralize the valve or control means 58. The mechanism further includes means for isolating the link 70 from the bucket 22 whenever the boom 18 drops below a predetermined lower position so that the bucket can be controlled manually.

As shown in FIG. 1, the first position for the shaft 200 is defined an adjustable stop 250 disposed in the path of an arm 252 (FIG. 6) fixed for rotation with the shaft 200. Biasing means 254 (FIG. 4) normally urges the arm 252 into engagement with the stop 250 to define the first position for the shaft. The biasing means 254 (FIGS. 4 and 6) is in the form of a cable 256 anchored at one end to the shaft 200 through a hub 258. The cable is entrained over a-pulley 260 freely rotatable on a bracket 262 with the opposite end of the cable anchored to a piston 264 slidably supported in a cylinder 266. The piston 264 is biased to an uppermost position (shown in FIG. 4) by a spring 268. Thus, the biasing means 254 normally urges the shaft 200 to a maximum counterclockwise rotated position wherein the arm 252 engages the stop or abutment 250. The arm 252 contacts the stop 250 when the bucket is pivoted a few degrees past the normal digging attitude to prevent the pivotal connection between arm 222 and link 240 from passing over center.

The mechanism for defining the second limit position for the shaft, corresponding to the maximum roll-back position for the bucket, includes means cooperating with the first linkage means, consisting of arm 204 and link 206, associated with one end of link 70 to automatically move the link 70 and the valve 58 to a neutral position. The maximum roll-back position of the bucket is maximum rearward pivoted position to which the bucket may be pivoted without danger of dumping the contents of the bucket onto the operator and/or the vehicle. This means or mechanism also includes means cooperating with the manual linkage system to move the opposite end of the link 70 to a neutral position.

The mechanism to prevent pivoting of the bucket beyond an extreme position includes first anti-roll-back stop means 270 operatively coupling the shaft 200 to the manual control means 120 when the lever 124 is in a roll-back actuated position and second anti-roll-back stop means 272 cooperating with the links 204 and 206 when the friction device is uncoupled to automatically move both ends of link 70 to a neutral position when the desired maximum bucket position is reached.

The first stop means 270 includes an arm 274 (FIGS. 4 and 6) fixed to the shaft 200 and a link 276 freely rotatable on the shaft 200 with the outer end of the link 276 being connected to a hub 277 of the shaft assembly 142 through an arm 278 and a link 280 and the hub 277 also has arm 150 secured thereto. The arm 276 has an adjustable stop 282 supported thereon and disposed in the path of the arm 274. Thus, when the bucket reaches a maximum roll-back position, the arm 274 will engage stop 282 and will rotate the arm 276 and the corresponding end of the link 70 from a lowered operative position to a neutral position thereby moving the valve to a neutral condition.

Before the operation of the second anti-roll-back stop means 272 can be comprehended, it will be necessary to describe the operative interrelationship between the manual control means 120 and the automatic control means 122 when the manual control means and more specifically the control lever 124 is moved in either direction from its neutral condition to extend or retract the control valve 58 and pivot the bucket in opposite directions. This operative interconnection is arranged in such a manner that the operator may set any desired angular relationsnhip of the bucket relative to a predetermined reference plane by mere manipulation of the control lever 124 from a neutral position. This is accomplished by automatically uncoupling the first linkage means (arm 204 and link 206) from the remainder of sensing means 122 to allow the bucket to be pivoted without feeding a signal to the control valve 58.

The means for uncoupling the first linkage means from the remainder of the sensing means includes a switch 300 (FIGS. 4 and 6) supported on an arm 302 which in turn is supported on a hub 304 forming part of the shaft assembly 142 with the arm 144 secured thereto. A second hub 306, forming part of the shaft assembly 142 and rotatable with hub 277 has a second arm 308 secured thereto and located in alignment with arm 302. The hub 306 further includes an actuating member 310 disposed in the path of an actuating arm 312 forming part of the switch 300. First and second sensor springs 314 and 316 are operatively interposed between the opposite ends of the respective arms 302 and 308 to maintain the arms and, thus, the hub 304, as well as the control lever 124 in a neutral position. However, manual pivotal movement of the control layer 124 will rotate hub 304 on the shaft 143 to acutate or open the switch 300. The rotation will also cause hub 277 to rotate after the springs 314 and 316 have been compressed a predetermined amount. To insure that the hubs 277 and 304 will move as a unit, it is desirable to have adjustable stops carried by one of the arms 302 and 308 and engaged by the other of the arms.

The switch 300 is incorporated in an electral circuit 320 (FIG. 8) which includes a battery 322 and the clutch 202. The circuit 320 further includes a normally closed second switch 324 (to be described later) with the opposite end of the circuit being suitably grounded at 326. If desired, the ignition switch 328 for the vehicle may also be incorporated into the circuit so that the circuit is interrupted whenever the vehicle is shut down.

Assuming switches 324 and 328 to be closed and the control lever in the neutral condition, switch 300 will be closed and the circuit 320 will energize the coupling means or clutch 202 to provide an operative connection between the bucket and the link 70. However, if the control lever 124 is moved in either direction from its neutral condition, the switch 300 will be moved from the normally closed condition to an open condition interrupting the circuit to the coupling means 202 thereby interrupting the connection between the bucket 22 and link 70. This will allow the biasing means 72, cooperating with the end of the link having the link 206 connected thereto, to automatically move the end of the link to the neutral condition and allow the bucket to be pivoted exclusively by the manual lever. During such manual control, the friction element 210, shaft 200 and second linkage means move with the pivoting of the bucket (within limits to be described later) while the arm 204 and link 206 remain fixed. However, when the control lever is returned to the neutral condition, which may be accomplished by mere release of the lever to allow the sensor springs 314 and 316 as well as the spring assembly 72 cooperating with the associated end of the link 70 to move the control linkage to a neutral condition. When the control linkage reaches a neutral condition, the switch 300 is again closed to operatively couple the two elements 210 and 212 of the coupling means 202 thereby connecting link 204 to the shaft 200. With this arrangement, the link or arm 204 may be coupled to the shaft in any one of a plurality of angular positions. The angular position of the link 204 on the shaft 200 will thereafter define a desired angular orientation relative to a fixed reference plane at which the bucket will be automatically maintained after the control lever is moved to the neutral condition.

Returning now to the second anti-roll-back stop means 272, this anti-roll-back stop means will only become operative when l the manual control lever is in a position corresponding to rolling back or counterclockwise rotation of the bucket on the boom (as viewed in FIG. 1) and (2) the bucket reaches a maximum angular position. As was described above, the arm 204 and link will be maintained in a set position by the spring assembly 72. However, should the bucket reach the maximum roll-back position. a stop 340 carried by the anchor 258 will engage the link 204 to insure that the associated end of the link 70 will be in a neutral position. At the same time, the arm 274 will engage stop 282 and automatically cause the manual control end of link 70 to be moved to a neutral condition. Stated another way, when the bucket reaches a maximum angular position relative to a fixed reference plane, the manual means and the automatic sensing means 122, respectively, will become interlocked to automatically move opposite ends of the link 70 to a neutral position. 11

According to another aspect of the present invention, the automatic sensing means will also automatically become inoperative when the boom or lift arm 18 is moved to a predetermined lowered position to allow pivoting of the bucket by the manual control means exclusively. This is accomplished by switch 324 (FIGS. 1 and 8) incorporated in the electric circuit 320 for the coupling means 202 with the switch 324 fixed to the boom 18. A stop 350 is fixedly secured to the bell crank 222 and is disposed in the path of an actuating arm 352, forming part of the switch 324. Thus, when the boom or lift arms 18 reach a predetermined lowered, pivoted position, the normally closed switch 324 is opened to automatically uncouple the link 204 from the shaft 200. This will occur substantially simultaneous to the linkage 50, 54 and the fluid ram 40 engaging stops (not shown) which define a maximum position for the bucket 22.

OPERATION The method of operation and the operation of the apparatus will now be described. Assuming the control valve 58 to be in a neutral condition and the bucket in the position shown in FIG. 1, and further assuming that the arm 252 is spaced from the stop 250, retraction of the fluid ram 26 through actuation of the control lever about a pivot axis, defined by shaft 126 will lower the boom 18. When the boom 18 starts to lower, the linkage 228 and 230 will produce clockwise rotation, as viewed in FIG. 1, of the bell crank 222 to rotate shaft 200. The rotation of the shaft 200 will be transmitted through links 204 and 206 to move link 70 from the solid line to the lower dotted line position of FIG. 10 and actuate the control valve to pivot the bucket 22 in a clockwise direction, as viewed in FIG. 1, and maintain the bucket 22 at a desired angular orientation. When the bucket is returned to the desired orientation relative to fixed reference plane P the link 70 is returned to the solid line position of FIG. 11, to neutralize the valve. On the other hand, raising of the boom 18 will rotate the shaft 200 in an opposite direction and move link 70 downward to the position shown in dotted line in FIG. 10 to acutate control valve 58 and pivot the bucket in a counterclockwise direction as viewed in FIG. 1. With this control, the angle A, defined between the longitudinal axis of the link 52 and a vertical reference plane or fixed reference plane P, will be maintained at a fixed value thereby maintaining the bucket 22 in a level condition as the boom 18 is raised and lowered. During the automatic control cycle, the opposite end of link 70 is maintained in a neutral position by spring assembly 72.

The angular relation A of the link 50, more particularly the parallelogram linkage including links 50, 232 and 234, defines the piovted position of the bucket 22. This desired angular orientation may readily be set at the will of the operator by movement of the control lever in opposite directions from a neutral position about the pivot axis 128. Movement of the control lever to an operative position, will open switch 300 to disconnect the coupling elements 210 and 212 and simultaneously actuate the control valve through arm I50 and link 152. While the control lever is in an actuated condition, the link 204 will be maintained in a fixed condition by the spring assembly 72 acting through the link 206, and the bucket will be pivoted in either direction, dependent upon the position of the control lever, which will cause relative rotation between the shaft 200 and the link 204. However, should the control lever be released, the spring assembly 72 acting on the manual end of the link will move the control lever, as well as the control valve, to a neutral position. During such movement, the switch 300 will again be actuated and the arm 204 will be coupled to the shaft 200 in a position corresponding to the angular position of the bucket relative to the reference plane P at that time. Thus, any angle A, within limits, may readily be set by the operator by manipulation of the control lever.

The first maximum oriented angle A is defined by the first limit position of the shaft 200 when the arm 252 engages the stop 250 while the second maximum oriented angle is defined by the second position of the shaft wherein the first and/or second stop means 270 and 272 are engaged to force both ends of the link 70 to a neutral position when the bucket is in the first limit position for the shaft 200, defining the first maximum oriented angle, the second linkage means connecting the shaft 200 to the bucket 22 incorporating the telescoping linkage 228 which will accommodate pivotal movement of the bucket 22 independent of the sensing means 122 when the bucket is pivoted beyond this maximum angular position. Such an arrangement is necessary to allow dumping of the contents of the bucket 22 without having the sensing mechanism operative.

By way of example, the first maximum angle defined by the first position of the shaft 200 where arm 252 is in engagement with the stop 250 may define an angle with respect to the reference plane P which is slightly greater than the normal return-to-dig angle for the bucket 22. The second extreme angular position may be the maximum desired pivoted position or roll-back position of the bucket relative to the fixed reference plane P. With such an arrangement, the automatic sensing means may be set to maintain the bucket 22 at any desired angle between return-todig angular position and the maximum roll-back angular position.

As was indicated above, the sensing mechanism is disconnected from the link 70 when the manual control is actuated, which will allow normal manual control of the bucket through the control lever 124 without any feedback through the linkage. During manual control, the left-hand end of link 70 is pivoted about the fixed right-hand end as viewed in FIGS. 11 and 12 to be moved to above and below the solid line to position the dotted line positions of FIGS. 11 and 12. When the link 70 is above the solid line neutral position the bucket is being pivoted toward the dumping position while movement of the link below the neutral, solid line position will pivot the bucket towards the rolled back position. Normally, during such movement, the stop elements of the respective stop means are spaced from each other (as shown in FIG. 11). However, when the bucket reaches a maximum roll-back position both stop means will become engaged to move both ends of the link to a neutral position (FIG. 12).

While the control mechanism has been described in connection with a bucket pivoted on a boom, the mechanism is capable of controlling the angular relation of various types of tools pivot on a boom such as a fork lift, or a logging device and these devices are all encompassed in the term unit in the appended claims.

Thus the present invention provides a control for a bucket valve which has great versatility and can readily be adjusted to automatically maintain the bucket at any desired angular relation relative to a fixed reference plane.

What is claimed is:

l. A method of controlling the angular orientation of a material handling unit relative to a fixed reference plane while the unit is pivotally supported on a boom and the unit is raised and lowered by swinging the boom about a fixed pivot axis and in which the unit is pivoted on a boom by moving a control valve in opposite directions from a neutral condition to supply fluid from a source to a ram located between the unit and boom and movement of the control valve is controlled by a manually controlled lever operatively connected to the valve and a sensing mechanism interposed between the valve and unit, comprising actuating said control valve by said manual control lever to supply fluid to said ram while simultaneously disconnecting the sensing mechanism from the control valve so that said control valve is controlled by said lever independent of the sensing mechanism, returning said control valve to a neutral condition with said lever and simultaneously setting the sensing mechanism to maintain the unit at one of a plurality of angular orientations relative to the fixed reference plane, sensing any deviations of the unit from the selected angular orientation with the sensing mechanism which results from swinging the boom; and actuating the control valve with the sensing mechanism to supply fluid to said ram and maintain the unit at the selected angular orientation.

2. The method as defined in claim 1, returning said control valve to a neutral condition with said sensing mechanism when said unit is being controlled by said manual member and the angular orientation reaches a maximum level.

3. The method as defined in claim 1, including the step of rendering the sensing mechanism inoperative when the boom reaches a predetermined lowered position so that said control valve may be controlled exclusively by said control lever. 

1. A method of controlling the angular orientation of a material handling unit relative to a fixed reference plane while the unit is pivotally supported on a boom and the unit is raised and lowered by swinging the boom about a fixed pivot axis and in which the unit is pivoted on a boom by moving a control valve in opposite directions from a neutral condition to supply fluid from a source to a ram located between the unit and boom and movement of the control valve is controlled by a manually controlled lever operatively connected to the valve and a sensing mechanism interposed between the valve and unit, comprising actuating said control valve by said manual control lever to supply fluid to said ram while simultaneously disconnecting the sensing mechanism from the control valve so that said control valve is controlled by said lever independent of the sensing mechanism, returning said control valve to a neutral condition with said lever and simultaneously setting the sensing mechanism to maintain the unit at one of a plurality of angular orientations relative to the fixed reference plane, sensing any deviations of the unit from the selected angular orientation with the sensing mechanism which results from swinging the boom; and actuating the control valve with the sensing mechanism to supply fluid to said ram and maintain the unit at the selected angular orientation.
 2. The method as defined in claim 1, returning said control valve to a neutral condition with said sensing mechanism when said unit is being controlled by said manual member and the angular orientation reaches a maximum level.
 3. The method as defined in claim 1, including the step of rendering the sensing mechanism inoperative when the boom reaches a predetermined lowered position so that said control valve may be controlled exclusively by said control lever. 